blob: ff833f97b95c2fe3243c5961fecbd79f148a8e8b [file] [log] [blame]
/***
This file is part of avahi.
avahi is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
avahi is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with avahi; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdlib.h>
#include <avahi-common/timeval.h>
#include <avahi-common/malloc.h>
#include "query-sched.h"
#include "log.h"
#define AVAHI_QUERY_HISTORY_MSEC 100
#define AVAHI_QUERY_DEFER_MSEC 100
typedef struct AvahiQueryJob AvahiQueryJob;
typedef struct AvahiKnownAnswer AvahiKnownAnswer;
struct AvahiQueryJob {
unsigned id;
int n_posted;
AvahiQueryScheduler *scheduler;
AvahiTimeEvent *time_event;
int done;
struct timeval delivery;
AvahiKey *key;
/* Jobs are stored in a simple linked list. It might turn out in
* the future that this list grows too long and we must switch to
* some other kind of data structure. This needs further
* investigation. I expect the list to be very short (< 20
* entries) most of the time, but this might be a wrong
* assumption, especially on setups where traffic reflection is
* involved. */
AVAHI_LLIST_FIELDS(AvahiQueryJob, jobs);
};
struct AvahiKnownAnswer {
AvahiQueryScheduler *scheduler;
AvahiRecord *record;
AVAHI_LLIST_FIELDS(AvahiKnownAnswer, known_answer);
};
struct AvahiQueryScheduler {
AvahiInterface *interface;
AvahiTimeEventQueue *time_event_queue;
unsigned next_id;
AVAHI_LLIST_HEAD(AvahiQueryJob, jobs);
AVAHI_LLIST_HEAD(AvahiQueryJob, history);
AVAHI_LLIST_HEAD(AvahiKnownAnswer, known_answers);
};
static AvahiQueryJob* job_new(AvahiQueryScheduler *s, AvahiKey *key, int done) {
AvahiQueryJob *qj;
assert(s);
assert(key);
if (!(qj = avahi_new(AvahiQueryJob, 1))) {
avahi_log_error(__FILE__": Out of memory");
return NULL;
}
qj->scheduler = s;
qj->key = avahi_key_ref(key);
qj->time_event = NULL;
qj->n_posted = 1;
qj->id = s->next_id++;
if ((qj->done = done))
AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->history, qj);
else
AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->jobs, qj);
return qj;
}
static void job_free(AvahiQueryScheduler *s, AvahiQueryJob *qj) {
assert(s);
assert(qj);
if (qj->time_event)
avahi_time_event_free(qj->time_event);
if (qj->done)
AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->history, qj);
else
AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->jobs, qj);
avahi_key_unref(qj->key);
avahi_free(qj);
}
static void elapse_callback(AvahiTimeEvent *e, void* data);
static void job_set_elapse_time(AvahiQueryScheduler *s, AvahiQueryJob *qj, unsigned msec, unsigned jitter) {
struct timeval tv;
assert(s);
assert(qj);
avahi_elapse_time(&tv, msec, jitter);
if (qj->time_event)
avahi_time_event_update(qj->time_event, &tv);
else
qj->time_event = avahi_time_event_new(s->time_event_queue, &tv, elapse_callback, qj);
}
static void job_mark_done(AvahiQueryScheduler *s, AvahiQueryJob *qj) {
assert(s);
assert(qj);
assert(!qj->done);
AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->jobs, qj);
AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->history, qj);
qj->done = 1;
job_set_elapse_time(s, qj, AVAHI_QUERY_HISTORY_MSEC, 0);
gettimeofday(&qj->delivery, NULL);
}
AvahiQueryScheduler *avahi_query_scheduler_new(AvahiInterface *i) {
AvahiQueryScheduler *s;
assert(i);
if (!(s = avahi_new(AvahiQueryScheduler, 1))) {
avahi_log_error(__FILE__": Out of memory");
return NULL; /* OOM */
}
s->interface = i;
s->time_event_queue = i->monitor->server->time_event_queue;
s->next_id = 0;
AVAHI_LLIST_HEAD_INIT(AvahiQueryJob, s->jobs);
AVAHI_LLIST_HEAD_INIT(AvahiQueryJob, s->history);
AVAHI_LLIST_HEAD_INIT(AvahiKnownAnswer, s->known_answers);
return s;
}
void avahi_query_scheduler_free(AvahiQueryScheduler *s) {
assert(s);
assert(!s->known_answers);
avahi_query_scheduler_clear(s);
avahi_free(s);
}
void avahi_query_scheduler_clear(AvahiQueryScheduler *s) {
assert(s);
while (s->jobs)
job_free(s, s->jobs);
while (s->history)
job_free(s, s->history);
}
static void* known_answer_walk_callback(AvahiCache *c, AvahiKey *pattern, AvahiCacheEntry *e, void* userdata) {
AvahiQueryScheduler *s = userdata;
AvahiKnownAnswer *ka;
assert(c);
assert(pattern);
assert(e);
assert(s);
if (avahi_cache_entry_half_ttl(c, e))
return NULL;
if (!(ka = avahi_new0(AvahiKnownAnswer, 1))) {
avahi_log_error(__FILE__": Out of memory");
return NULL;
}
ka->scheduler = s;
ka->record = avahi_record_ref(e->record);
AVAHI_LLIST_PREPEND(AvahiKnownAnswer, known_answer, s->known_answers, ka);
return NULL;
}
static int packet_add_query_job(AvahiQueryScheduler *s, AvahiDnsPacket *p, AvahiQueryJob *qj) {
assert(s);
assert(p);
assert(qj);
if (!avahi_dns_packet_append_key(p, qj->key, 0))
return 0;
/* Add all matching known answers to the list */
avahi_cache_walk(s->interface->cache, qj->key, known_answer_walk_callback, s);
job_mark_done(s, qj);
return 1;
}
static void append_known_answers_and_send(AvahiQueryScheduler *s, AvahiDnsPacket *p) {
AvahiKnownAnswer *ka;
unsigned n;
assert(s);
assert(p);
n = 0;
while ((ka = s->known_answers)) {
int too_large = 0;
while (!avahi_dns_packet_append_record(p, ka->record, 0, 0)) {
if (avahi_dns_packet_is_empty(p)) {
/* The record is too large to fit into one packet, so
there's no point in sending it. Better is letting
the owner of the record send it as a response. This
has the advantage of a cache refresh. */
too_large = 1;
break;
}
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) | AVAHI_DNS_FLAG_TC);
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_ANCOUNT, n);
avahi_interface_send_packet(s->interface, p);
avahi_dns_packet_free(p);
p = avahi_dns_packet_new_query(s->interface->hardware->mtu);
n = 0;
}
AVAHI_LLIST_REMOVE(AvahiKnownAnswer, known_answer, s->known_answers, ka);
avahi_record_unref(ka->record);
avahi_free(ka);
if (!too_large)
n++;
}
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_ANCOUNT, n);
avahi_interface_send_packet(s->interface, p);
avahi_dns_packet_free(p);
}
static void elapse_callback(AVAHI_GCC_UNUSED AvahiTimeEvent *e, void* data) {
AvahiQueryJob *qj = data;
AvahiQueryScheduler *s;
AvahiDnsPacket *p;
unsigned n;
int b;
assert(qj);
s = qj->scheduler;
if (qj->done) {
/* Lets remove it from the history */
job_free(s, qj);
return;
}
assert(!s->known_answers);
if (!(p = avahi_dns_packet_new_query(s->interface->hardware->mtu)))
return; /* OOM */
b = packet_add_query_job(s, p, qj);
assert(b); /* An query must always fit in */
n = 1;
/* Try to fill up packet with more queries, if available */
while (s->jobs) {
if (!packet_add_query_job(s, p, s->jobs))
break;
n++;
}
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_QDCOUNT, n);
/* Now add known answers */
append_known_answers_and_send(s, p);
}
static AvahiQueryJob* find_scheduled_job(AvahiQueryScheduler *s, AvahiKey *key) {
AvahiQueryJob *qj;
assert(s);
assert(key);
for (qj = s->jobs; qj; qj = qj->jobs_next) {
assert(!qj->done);
if (avahi_key_equal(qj->key, key))
return qj;
}
return NULL;
}
static AvahiQueryJob* find_history_job(AvahiQueryScheduler *s, AvahiKey *key) {
AvahiQueryJob *qj;
assert(s);
assert(key);
for (qj = s->history; qj; qj = qj->jobs_next) {
assert(qj->done);
if (avahi_key_equal(qj->key, key)) {
/* Check whether this entry is outdated */
if (avahi_age(&qj->delivery) > AVAHI_QUERY_HISTORY_MSEC*1000) {
/* it is outdated, so let's remove it */
job_free(s, qj);
return NULL;
}
return qj;
}
}
return NULL;
}
int avahi_query_scheduler_post(AvahiQueryScheduler *s, AvahiKey *key, int immediately, unsigned *ret_id) {
struct timeval tv;
AvahiQueryJob *qj;
assert(s);
assert(key);
if ((qj = find_history_job(s, key)))
return 0;
avahi_elapse_time(&tv, immediately ? 0 : AVAHI_QUERY_DEFER_MSEC, 0);
if ((qj = find_scheduled_job(s, key))) {
/* Duplicate questions suppression */
if (avahi_timeval_compare(&tv, &qj->delivery) < 0) {
/* If the new entry should be scheduled earlier,
* update the old entry */
qj->delivery = tv;
avahi_time_event_update(qj->time_event, &qj->delivery);
}
qj->n_posted++;
} else {
if (!(qj = job_new(s, key, 0)))
return 0; /* OOM */
qj->delivery = tv;
qj->time_event = avahi_time_event_new(s->time_event_queue, &qj->delivery, elapse_callback, qj);
}
if (ret_id)
*ret_id = qj->id;
return 1;
}
void avahi_query_scheduler_incoming(AvahiQueryScheduler *s, AvahiKey *key) {
AvahiQueryJob *qj;
assert(s);
assert(key);
/* This function is called whenever an incoming query was
* received. We drop scheduled queries that match. The keyword is
* "DUPLICATE QUESTION SUPPRESION". */
if ((qj = find_scheduled_job(s, key))) {
job_mark_done(s, qj);
return;
}
/* Look if there's a history job for this key. If there is, just
* update the elapse time */
if (!(qj = find_history_job(s, key)))
if (!(qj = job_new(s, key, 1)))
return; /* OOM */
gettimeofday(&qj->delivery, NULL);
job_set_elapse_time(s, qj, AVAHI_QUERY_HISTORY_MSEC, 0);
}
int avahi_query_scheduler_withdraw_by_id(AvahiQueryScheduler *s, unsigned id) {
AvahiQueryJob *qj;
assert(s);
/* Very short lived queries can withdraw an already scheduled item
* from the queue using this function, simply by passing the id
* returned by avahi_query_scheduler_post(). */
for (qj = s->jobs; qj; qj = qj->jobs_next) {
assert(!qj->done);
if (qj->id == id) {
/* Entry found */
assert(qj->n_posted >= 1);
if (--qj->n_posted <= 0) {
/* We withdraw this job only if the calling object was
* the only remaining poster. (Usually this is the
* case since there should exist only one querier per
* key, but there are exceptions, notably reflected
* traffic.) */
job_free(s, qj);
return 1;
}
}
}
return 0;
}